Polarized reed relay



*My 5, 1970 MASAO'TAKAMURA ETAL I 3,510,812

POLARIZED REED RELAY Filed April 19, 1968 7,111,111.11. "11111 lll F. Ei INVENTORS d Mosao Tokamuro Ig f Koisuhro Kom l Tokeo Shnohurcl HsuhideKikuchi Sodoyuk Mifsuhosh ATTORNEYS United States Patent O U.S. Cl.335-153 10 Claims ABSTRACT OF THE DISCLOSURE Polarized reed relayapparatus is provided which is highly stable and in operation requiresonly relatively low current magnitudes to change the state thereof. Inone embodiment, the state of the reed switch is determined by themagnetic condition of remanent material disposed in a parallelrelationship therewith. The unitary remanent material is magneticallyseparated into two portions wherein a first portion may be magneticallydriven to a first or second state and the second portion thereof inmaintained in a first magnetically polarized state. The reed switch willbe maintained in the closed condition when said first portion ismagnetized in the same direction as said second portion and the openposition will be established when said first portion is magnetized inanother direction.

This invention relates to magnetic switch or relay apparatus and, moreparticularly, to polarized reed relay apparatus of the latching typehaving a series magnetic circuit.

Although this invention is not limited to use with any particularapparatus or in conjunction with any specified combination, thepolarized reed relay apparatus according to the present invention admitsof wide use within telephone switching systems and electronic equipmentin general, and has particular application as a channel cutoff relay inelectronic switching systems.

Present day polarized reed relay apparatus normally comprises a reedswitch, a magnetic shunt plate for mag netically separating the reedswitch into two portions in the longitudinal direction, a permanentmagnet means disposed on one of said two portions, a semihard magnetmaterial disposed on the other of said two portions, and coil meanswound about said semihard magnetic material. The operation of thesedevices has, however, suffered because the magnetic coupling therein isinherently loose due to the presence and location of the shunt plateutilized therein. In addition, when the semihard magnetic materialpresent in such devices is magnetized in the sarne direction as thepermanent magnet means, a demagnetizing field is present in the vicinityof the end portions of these polarized elements which face each otherover said magnetic shunt plate. This demagnetizing field thereby causesa weakening of the magnetic field in the area of the shunt plate whichmanifests itself in a corresponding reduction of the field intensity atthe contact portions of the reed switch. Thus, to insure the properoperation of the polarized reed relay apparatus of the prior art, coilmeans having large ampere-turn products were necessary and such largeampere-turn products were normally achieved by using relatively highcurrent magnitudes with their inherent expense and disadvantges.

Therefore, it is a primary object of this invention to providepolarized, latching reed relay apparatus which is operable withrelatively low current magnitudes, is highly stable in operation, and isnot subject to faulty operation due to the non-uniform magnetization ofits respective ice remanent members. Various other objects andadvantages of the invention will become clear from the followingdetailed description of the embodiments disclosed herein, and the novelfeatures of the present invention will be particularly pointed out inconnection with the appended claims.

In accordance with the invention, polarized, latching reed relayapparatus is provided wherein a reed switch is operated by themagnetizing force applied by a semihard magnetic material disposed in aparallel relationship with said reed switch; the semihard magneticmaterial being adapted for magnetic separation into first and secondportions whereby said second portion thereof is polarized by amagnetically hard material in a first direction while the first portionthereof is acted upon by a field applying means which is capable ofmagnetizing said first portion in either a first or second direction.The invention will be more clearly understood by reference to thefollowing detailed description of several embodiments thereof inconjunction with the accompanying drawings in which:

FIGS. 1(a)l(b) show a first embodiment of the polarized reed relayapparatus according to this invention wherein FIG. 1(11) is a detailedstructural view, partially in section, of said first embodiment, andFIG. 1(b)-l (d) illustrate various coercive force distributions alongthe longitudinal axis of the FIG. l(a) structure; and

FIG. 2 is a detailed structural view, partially in section, of a secondembodiment of the polarized reed relay apparatus according to thisinvention.

Referring now to the drawings and more particularly to FIG. l thereof,there is shown a first embodiment of the polarized reed relay apparatusaccording to the present invention. The apparatus depicted in FIG. 1(a)comprises a reed switch 1, magnetic members 2 and 2', a magnetic shuntplate 3, magnetomotive force applying means 4-4; and permanent magnetmeans 5 and 5. The depicted reed switch 1 may take the well known formwherein two overlapping, thin magnetic reeds 1 are encapsulated within asealed glass chamber. Magnetic members 2 and 2 which may take the formof two fiat bars of magnetic material, are mounted in a parallelrelationship with the thin magnetic reeds 1 on the outside of the glasschamber. The magnetic members 2 and 2 are preferably formed of asemihard magnetic material whose domains are capable of remaining in astable, aligned remanent condition once they have been subjected to anexternal magnetic field, but which domains are sufficiently mobile sothat their orientation may be reversed to a second stable, alignedcondition by an oppositely directed external field applied subsequently.The magnetic members 2 and 2 have located at their approxiate centers, amagnetic shunt plate which is made of soft magnetic material. Themagnetic shunt plate 3 is positioned so that the magnetic members 2 and2 may be magnetically separated, on either Side of the central axis ofsaid shunt plate 3, into two adjacent magnetic portions. The twoadjacent portions thereby formed are each located opposite one of thetwo thin magnetic reeds 1' which reeds in turn overlap in the area ofthe magnetic shunt plate 3. A first magnetic portion of each of themagnetic members 2 and 2', as herein shown to the right of the magneticshunt plate 3, is wound by a magnetomotive force applying means 4 4'which may be an ordinary exciting coil, as indicated by thecross-sectional showing thereof which is annotated 4-4. Themagnetomotive force applying means 4-4 is connected in the usual mannerto a standard current driver, not shown herein, so that current pulsesmay be applied thereto and thus positive or negative current caused toflow therein in either a first or second direction to thereby establisha first or second axial field. Such first or second fields willrespectively be directed toward or away from said magnetic shunt plate3. The coercive force distribution along each of said magnetic members 2and 2', as applied solely by the magnetomotive force applying means4-4', when energized, is shown in FIG. l(b). The effect of magneticshunt plate 3 is also clearly demonstrated in FIG. 1(1)) wherein therapid dropoff in the magnitude of the coercive force on the oppositeside of the magnetic plate 3 is clearly indicated by the shaded portionthereof.

A second magnetic poriton of each of the magnetic members 2 and 2', asherein shown to the left of the magnetic shunt plate 3, has its domainsunidirectionally aligned by the magnetic and mechanical coupling theretoof permanent magnet means and 5 respectively. The permanent magnet means5 and 5' each preferably exhibit a large amount of residual magnetismand hence manifest a coercive force which is substantially larger thanthat of the magnetic members 2 and 2. This coercive force should besufficiently large so that neither the permanent magnet means 5 or 5' orthe second magnetic portions of the magnetic members 2 or 2', which arerespectively coupled thereto, will be demagnetized by the leakage fluxproduced by the exciter coil 4-4' as indicated by the shaded portion ofFIG. l(b). In practice, when close coupling is achieved between thepermanent magnet means 5 and 5' and the magnetic members 2 and 2', thevalues of the coercive force and the demagnetizing factor in thepermanent magnet means 5 and 5 should be about three times greater thanthat of the magnetic members 2 and 2'.

In operation, the apparatus shown in the FIG. l embodiment is a basicbistable switching device which may be set in either the opened orclosed switch position and thereafter retain this position unless thecondition thereof is subsequently altered. The reed switch 1 operates inthe well known manner such that the thin magnetic reeds 1' therein willbe drawn together in response to flux present between their overlappingportions and will separate in the absence of flux between saidoverlapping portions. Thus an open or closed reed switch condition isachieved. The presence or obsence of flux in the overlapping portionsthereof as will be seen hereinafter, is determined by the magneticcondition of the magnetic members 2 and 2' and more particularly therelative magnetic conditions of the respective first and second mangeticportions thereof.

The second magnetic portion of each of the magnetic members 2 and 2', asshown herein to the left of the magnetic shunt plate 3, is mechanicallyand magnetically coupled, as aforesaid, by the permanent magnet means 5and 5' respectively, and is thus closely coupled thereto.

The continuous application of the coercive force manifested by thepermanent magnet means 5 and 5' to the respective second magneticportions of each of the magnetic members 2 and 2' causes the magneticdomains therein to be aligned in the direction of the constant magneticfield applied thereto. This direction of orientation is indicated by thearrows shown in the left hand portion of FIGS. 1\(a)1 (d). The secondmagnetic portions of each of the magnetic members 2 and 2' are,therefore, uniformly magnetized in the direction of the illustratedleft-hand arrows and thus act to polarize the left hand portion of thereed switch 1 in the direction of the magnetic field applied thereby.This continuously applied field is indicated by the second quadrantportions of the coercive force distribution curves depicted in FIGS.1(c) and l(d).

The first magnetic portions of each of the magnetic members 2 and 2', asshown herein to the right of the magnetic shunt plate 3, are wound, asaforesaid, by a magnetomotive force applying means which is depicted asan ordinary exciting coil 4-4'. The standard current driver, not shownherein, which is connected in the usual :manner thereto, may beenergized by the actuation of ordinary switching apparatus normallyutilized therewith so as to apply current pulses of either a rst orsecond polarity, or in a first or second direction to the exciting coil4-4'. The application of current pulses to the exciting coil 4e4 of afirst or second polarity or in a first or second direction establishes,in the well known manner, first or second axial fields respectively inthe space linked by said exciting coil 4-4'. The direction of such firstor second axial fields is indicated by the right-hand arrows shown inFIGS. 1(0) and 1(d), respectively. The first magnetic portions of themagnetic members 2 and 2', are wound by said exciting coil 4-4 and thusthe magnetic domains therein will tend to align with the axial fieldsproduced thereby. Once the magnetic domains in said first portions havealigned with the applied magnetic field, the current driver may bede-energized as said first portions will retain, in the well knownmanner, the remanent -magnetic state to which it was switched. The firstmagnetic portions of each of the magnetic members 2 and 2' may be thusuniformly magnetized in either of said aforesaid first or seconddirections and may therefore act to polarize the right-hand portion ofthe reed switch 1 in the direction of the magnetic field appliedthereby. These fields are indicated by the portions of the coerciveforce distribution curves depicted in the first quadrant of FIG. 1(d)and the fourth quadrant of FIG. l(c).

The magnetic field generated by the exciting coil 4-4' will have littleor no effect on the second magnetic portions of each of the magneticmembers 2 and 2' :because the magnetically soft shunt plate 3 willshield said second portions therefrom and any leakage fiux which may beapplied thereto, as illustrated by the shaded portion of FIG. l(b), willbe of insufficient magnitude for the reasons stated above, to change theremanent state of said second portions. Thus, it is seen that althoughthe second manetic portions of each of the magnetic members 2 and 2' aremaintained by the permanent magnet means S and 5' in a first magneticstate, the first magnetic portions of each of the magnetic members 2 and2 may be remanently magnetized by the selective energization of theexciting coil 4-4' in either a first state which is the same as that ofsaid second portions or a second state, opposite to that of said secondportions.

When current pulses are applied to the exciting coil 4-4 so that thefirst magnetic portions of each of the magnetic members 2 and 2 areremanently magnetized in the first direction, both of said first andsecond magnetic portions of said magnetic members 2 andy 2 will bemagnetized in the first direction. This creates at least a remanentcondition in said first magnetic portions so that when the field appliedby the exciting coil 4-4 is turned off, the desired magnetic state will=be maintained. Since the magnetic domains in each of said first andsecond magnetic portions of said magnetic members 2 and 2' all tend toalign in the same direction, the magnetic domains at the Iboundarybetween said first and second portions, under the magnetic shunt plate3, will also tend to align in this direction due to normal domainpropagation. Thus the magnetic members 2 and 2' will tend to manifestthe open fiux path lof a single piece of aligned magnetic material.Accordingly, both of the magnetic reeds 1 of the reed switch 1 arelinked by a unidirection flux field which will cause the magnetic reeds1 therein to close at the overlapping portions thereof and to bemaintained in this closed condition until the coercive force appliedthereto is modified by a change in the state of the first portion ofsaid magnetic members 2-2'. The coercive force distribution along themagnetic reeds 1' when both of said first and second magnetic portionsof said magnetic members 2 and 2 are magnetized in the same condition isillustrated in FIG. 1(d). As can be seen by the inspection thereof, astable, uniform magnetizing force is applied to reed switch 1 tomaintain it in its closed condition.

If current is thereafter applied to the exciting coil 4,-4 S0 as toapply a magnetomotive force to the first mag.-

netic portions of the magnetic members 2 and 2' in the oppositedirection to thereby change their remanents state to the second statedescribed above, said iirst portions will be remanently magnetized in anopposite direction to that of the second portions of said magneticmembers 2 and 2'. The first and second portions of said magnetic members2 and 2' will thereby exhibit oppositely directed open iiux paths andthe sections of the magnetic members 2 and 2' underlying said magneticshunt plate 3 will tend toward a magnetically neutral state which servesas a buffer between the oppositely magnetized first and second portions.The right and left magnetic reeds of the reed switch 1 will thereby belinked by oppositely directed flux and the overlying conL tact portionsthereof will either not be linked fby the separate and oppositelydirected flux paths or if any fringing ux from one of said magneticportions happens to link said contact portions, it will be cancelled byfringing flux from the other of said magnetic portions. Thus, theoverlapping contact portions of the magnetic reeds 1' are linked by zeroeffective flux and the reed switch 1 is maintained in an open condition.The coercive force distribution along the magnetic reeds 1 when each ofsaid first and second magnetic portions of said magnetic members 2 and 2are oppositely magnetized is illustrated in FIG. 1(0). As can be seen byinspection thereof, a zero magnetizing force is present in the area ofthe contact portions of the magnetic reeds 1 so that said reed switch 1is readily maintained in the open condition. If it is thereafter desiredto close the reed switch 1, it is merely necessary to energize the eX-citing coil 4-4 with current pulses tending to drive said first magneticportions of said magnetic members 2 and 2 toward said first remanentstate.

'Ihus it is seen that the apparatus described in the FIG. l embodimentof the instant invention provides polarized latching relay apparatusthat is highly stable in each of its operating conditions and notsubject to faults due to the nonuniform magnetization of its respectivemagnetic members.

The apparatus as shown in the FIG. 2 embodiment of the present inventionillustrates multiple contact reed relay apparatus in accordance with theteachings of the invention. The depicted apparatus comprises rst andsecond reed switches and 10', magnetic member 12, a magnetic shunt plate13, magnetomotive force applying means 14, and permanent magnet means15. The reed switches 10 and 10 may again take the well known formdescribed in conjunction with FIG. l(a) wherein two overlapping, thinmagnetic reeds 11 and 11 are encapsulated within a sealed glass chamber.The magnetic member 12, which may take the same form and substance asdescribed with regard to FIG. 1(a), except that it is double thethickness of the single members disclosed therein, as shown, is mountedin a parallel relationship with the th-in magnetic reed pairs 11 and .11intermediate said reed switches 10 and 10'.

The magnetic member 12 has located at its approximate center, a magneticshunt plate 13 which is again made of soft magnetic material and servesto magnetically separate the two portions of the magnetic member 12 oneither side thereof. In addition, the magnetic shunt plate 13 isextended to the opposite -sides of the reed switches 10 and 10 toisolate the contact portions thereof from spurious fields which may becreated by the magnetomotive force applying means 14. A first magneticportion of the magnetic member 12 is wound by the magnetomotive forceapplying means 14 which again may take the form of an ordinary excitingcoil. The magnetomotive force applying means 14 is also connected, inthe usual manner, to a standard current driver, not shown herein, whichis capable of performing the same functions as was that described withregard to FIG. 1(a). The second magnetic portion of the magnetic member12 has its domains unidirectionally aligned 6 by the permanent magnetmeans 15 mechanically and magnetically coupled thereto. The permanentmagnet means 15 may take the same form and have the same characteristicsas that described with regard to FIG. 1(a).

In operation,l the multiple contact reed relay apparatus as shown inFIG. 2 has precisely the same mode and theory of operation as thatdescribed with regard to FIG. l. Here, however, the multidirectionalcharacteristc of the magnetic iiux path is taken advantage of to providefor the operation of a plurality of reed switches 10 and 10 in unison.Thus, when the first and second magnetic portions of the magnetic member12 are aligned in the same direction, both of the reed switches 10 and10' will be in the closed condition and will remain in this stable,closed condition until such time as the magnetic state of the rstmagnetic portion of the magnetic member 12 is reversed whereby said reedswitches will be opened. As will be obvious, additional reed switchesmay be incorporated into embodiments similar to that shown in FIG. 2 solong as the thickness of the magnetic member 12 is continuouslyincreased to provide additional magnetomotive force thereto.

Thus, the apparatus disclosed in the FIG. 2 embodiment of the presentinvention provides polarized multiple contact reed relay apparatus ofthe latching variety which is highly stable in operation and free frommagnetic operating deficiencies.

Although the described embodiments of the present invention have reliedupon the utilization of a magnetic shunt plate to shield and isolate thesecond magnetic portion of the magnetic member from rst magnetic portionof said member, it has been found that said magnetic shunt plate Iisunnecessary if the magnetic coupling between the permanent magnet meansand the magnetic member is close and the ratio of their respectivecoercive forces exceeds five. Furthermore, a substantial increase in thelength of the magnetic member with the retention of similar excitingwindings and permanent magnet means would seem to accomplish the sameresult. In addition, although the permanent magnet means have been shownin the disclosed embodiments as coextensive in areas with the secondportion of the magnetic member, such coincidence in area is notnecessary as the illustrated embodiments will operate satisfactorily ifonly 10% of the permanent magnet means is overlapped by the secondportion of magnetic member.

It will be noticed that the magnetic coupling between said first andsecond portions of said magnetic members approaches the ideal casebecause the entire coupling therebetween takes place through an integralpiece of magnetic material. Thus, low switching current pulses may beapplied to the exciting coil with their advantageous mode of operationand their inherent economy. Further, when both magnetic portions of themagnetic members are magnetized in the same direction, the magneticseparateness of said rst and second portions is destroyed therebycausing the magnetic members to exhibit a uniform, a stable magneticcondition.

It will thus be seen that the instant invention provides polarized,latching reed relay apparatus, operable at relatively low currentmagnitudes, which is highly stable in both of its switch positions andnot subject to faults due to non-uniform magnetization of its respectiveremanent members.

While the invention has been described in connection with two specificembodiments thereof, it will be understood that many modifications willbe readily apparent to one of ordinary skill in the art; and that thisapplication is intended to cover any adaptations or variations thereof.Therefore, it is manifestly intended that this invention be only limitedby the claims and the equivalents thereof.

We claim:

1. Polarized reed relay apparatus comprising:

reed switch means having at least first and second thin reed meansmounted therein, said thin reed means having portions thereof adaptedfor contact theref between; i i

'.mag'netic member .means disposed in a parallel relationship withsaidreed switch means, said magnetic member means exhibiting magnetichysteresis and the incident remanent magnetic properties thereof;

`means. magnetically dividing said reed switch means at the contactportions of said thin reedmeans, said magneticidividing means furtheracting to magnetically divide a first portionlof said magnetic membermeans from a second-portion thereof;

first magnetomotive field applying means mounted in an operativerelationship with said first portion of said magnetic member means, saidfirst magnetomotive field applying means adapted when energized toselectively drive said first portion of said magnetic member meanstoward a first or second-magnetic state; and

second magnetomotive field applying means magnetically coupled to saidsecond portion of said magnetic member means, said second magnetomotivefield applying means comprising permanent magnet means adapted tomaintain said second portion of said magnetic member means in a firstmagnetic state, whereby said reed switch means will be in a closedswitch condition when said first and second portions of said magneticmember means are each in said rst magnetic state and said reed switchmeans will be in an open switch condition when said first and secondportion of said magnetic member means are each in different magneticstates.

2. The apparatus of claim 1 wherein said second magnetomotive fieldapplying means is mechanically coupled to said second portion of saidmagnetic member means.

3. The apparatus of claim 2 wherein said first magnetomotive eldapplying means comprises coil means wound about said rst portion of saidmagnetic member means.

4. The apparatus 'of claim 3 wherein said means magnetically dividingsaid reed switch means comprises magnetic shunt plate means made ofmagnetically soft material.

5. The apparatus of claim 4 wherein said magnetic member means comprisesat least a first and second discrete magnetic member, said first andsecond discrete magnetic members being disposed on either side of saidreed switch means.

p 6. The apparatus'of claim 5 wherein said coil means is wound aboutsaid .first portion of eachofsaid first and second discrete magneticmembers and in addition thereto is wound about a portion of said reedswitch means.

7. The apparatus of claim 6 wherein said permanent magnet meansconstitutes at least first and second permanent magnet means fixedlymounted respectively to said second portion of each of said first andsecond discrete magnetic members.

8. The apparatus of claim 4 wherein said reed switch means having atleast first and second thin reed means mounted therein includes at leastfirst and second separate reed switches.

9. The apparatus of claim 8 wherein said magnetic member means comprisesa single bar of magnetic material interposed between said first andsecond separate reed switches.

10. The apparatus of claim 9 wherein said coil means is Wound solelyabout'said first portion'of said magnetic member and said permanentmagnet means is fixedly mounted to said second portion of said magneticmember.

References Cited UNITED STATES PATENTS 2,877,315V 3/1959 Oliver a335-153 3,075,059 1/1963 Bla'ha et al. 335--153 3,382,468 5/1968 Mattes335-153 BERNARD A. GILHEANY, Primary Examiner R. N. ENVALL, IR.,Assistant Examiner

